1. Field of the Invention
The present invention relates to a two-stage heating device for a handle of a vehicle such as a motorcycle, snowmobile, skibob, or the like.
2. Description of the Related Art
The drive""s hands of vehicles with handles are less dexterous when in a low temperature environment such as a snowfield, the Artic Zone, the Antarctic Zone, or a high mountain. The handles of vehicles such as motorcycles, snowmobiles, skibobs, or the like are made of rubber and thus apt to deteriorate and lose elasticity when used in the low temperature environment.
FIG. 1 of the drawings illustrates a tubular member 1 of a conventional handle with a heating device, and FIG. 2 is a sectional view of the conventional handle comprised of the tubular member 1 and a rubber jacket 2. A helical groove 13 is defined in an outer periphery of the tubular member 1 for receiving a heating coil 11. Thus, the rubber jacket 2 mounted around the tubular member 1 is heated by the heating coil 11 to warm the hands of the driver. Nevertheless, such a heating device can only provide a single stage heating. Namely, two-stage control of heating for controlling the temperature of the rubber jacket 2 in response to the temperature of the environment is impossible. If two heating coils are mounted in the same helical groove 13, short circuit could occur.
A handle in accordance with the present invention includes a tubular member including two parallel helical recessed portions formed on an outer periphery thereof, a rubber jacket mounted around the tubular member, and two heating coils of different heating efficiency being respectively mounted in the parallel helical recessed portions for heating the rubber jacket. Two-stage control of heating for controlling the temperature of the rubber jacket in response to the temperature of the environment is provided.
The parallel helical recessed portions are formed by four rows of protrusions formed on the outer periphery of the tubular member and extending along a direction parallel to a longitudinal axis of the tubular member.
In an embodiment of the invention, the tubular member is cylindrical. In another embodiment of the invention, the tubular member has a square section and four sides, with the four rows of protrusions being respectively formed on the four sides of the tubular member. In a further embodiment of the invention, the tubular member has a square section and four sides, with the four rows of protrusions being respectively formed on the four longitudinal edges of the tubular member.